High upfront cost may be a barrier to adopting chimeric antigen receptor T-cell therapy (CAR-T) for relapsed/refractory B cell lymphoma (BCL). Data on the real-world costs are limited. Using the Blue Cross Blue Shield Axis database, we evaluated 271 commercially insured patients who received CAR-T for BCL (median age: 58 years, men: 68%, diffuse large BCL: 87%, inpatient CAR-T: 85%). Our peri-CAR-T period of interest comprised -41 to + 154 days from CAR-T index, divided into seven 28-day intervals. Median total costs were $608,100 (interquartile range: $534,100-$732,800); 8.5% of patients had total costs >$1,000,000. Median cost of CAR-T products was $402,500, and median out-of-pocket copayment was $510. Monthly costs were highest during the month of CAR-T administration (median: $521,500), with median costs <$25,000 in all other 28-day intervals. Costs of CAR-T use were substantial, largely driven by product acquisition. Future studies should examine the relation between costs, access, and financial outcomes.